Mounting apparatus for panelboards



Oct. 18, 1966 z. J. KRUZIC ETAL MOUNTING APPARATUS FOR PANELBOARDS 2 Sheets-Sheet 1 Filed May 10, 1965 Fig. l.

Fig.2.

ww 4 A INVENTORS Zelko J. Kruzic 8 Paul Skulko BY fihxawl A, M

ATTORNEY WITNESSES J%U Oct. 18, 1966 Z- J. KRUZIC ETAL MOUNTING APPARATUS FOR PANELBOARDS Filed May 10, 1963 2 Sheets-Sheet 2 United States Patent 3,280,380 MOUNTING APPARATUS FOR PANELBOARDS Zelko J. Kruzic, New Brighton, and Paul Skalka, Beaver, Pa., assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed May 10, 1963, Ser. No. 279,495 12 Ciainls. (Cl. 317-119) This invention relates generally to mounting apparatus for panelboards and more particularly to improved means for lremovably mounting control devices on panelboards.

A general object of this invention is to provide improved means for removably mounting electrical control devices on panelboards.

Many pianelboards are constructed with a relatively large number of control devices mounted thereon. In order to reduce assembly time, it is desirable to provide panelboards that can be assembled with a minimum number of fastening members, such .as screws, that have to be separately worked by means of a tool.

Accordingly, another object of this invention is to provide improved means for removably mounting electrical control devices on a mounting plate without the use of separate fastening members such as screws between the control devices and the mounting plate.

In panelboards wherein a plurality of relays are mounted, it is sometimes desirable that the relays and, therefore, the control function can be readily changeable in the field. Thus, this invention has particular utility when it is utilized for the mounting of control relays. Ac co-rdingly, another object of this invention is to provide an improved panelboard with a plurality of readily removable relays mounted thereon.

A further object of this invention is to provide an im proved mounting plate comprising a press-worked sheet metal member that is economical to manufacture.

The invention both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description when read in conjunction with the accompanying drawings.

In said drawings:

FIGURE 1 is a plan view of part of a panelboard illustrating principles of the invention;

FIG. 2 is a plan view of the mounting plate seen in FIG. 1;

FIG. 3 is a sectional View taken along the line IIIIII of FIG. 2;

FIG. 4 is a sectional view taken along the line IVIV of FIG. 2;

FIG. 5 is a sectional view of the control device seen in FIG. 1 and taken generally along the line V-V of FIG. 6;

FIG. 6 is a sectional view taken generally along the line VI-VI of FIG. 5;

FIG. 7 is a plan view of the supporting plate seen in FIGS. 1, 5 and 6; and,

FIG. 8 is an end view of the supporting plate seen in FIG. 7.

Referring to the drawings, there is shown, in FIG. 1, part of a panelboard 1 comprising a panelboard backplate 2 and a plurality of mounting plates 3 mounted thereon. Since all three of the mounting plates 3 are of identical construction, only the center mounting plate 3 is fully shown; the two end mounting plates 3 being only partly shown. As can be seen in FIGS. 1 and 2, each of the mounting plates 3 has four openings 4 at the four corners thereof to receive four screws 5 that are used to secure the mounting plate 3 to the panelboard backplate 2. If desired, the mounting plate 3 could be welded or otherwise suitably attached to the backplate 2.

3,280,380 Patented Oct. 18, 1966 ice Each of the mounting plates 3 is adapted to have three electrical control devices 6 mounted on the generally flat mounting face of the mounting plate. Each of the electrical control devices 6 comprises a relay 7 and a rectangular supporting plate 8. The relay 7 is of the type that is described in more detail in the patent to Gustov Jakel, Patent No. 3,088,058, issued April 30, 1963.

As can be seen in FIGS. 5 and 6, the relay 7 comprises a housing comprising a base 13 and a cover 15, both of insulating material. The housing parts 13 and 15 are firmly held together as a unit by means of bolts (not shown). An E-shaped main magnet or core member 17 is supported, with its legs extending upwardly, in the housing base 13. A magnetizing winding, or coil, 19, that is disposed on a suitable spool 21 of insulating material, is positioned over the middle leg of the core member 17. An B-shaped armature 25 is provided to cooperate with the core member 17. The armature 25 is connected to an insulating contact carrier 27 by means of a bolt 29 that pivotally mounts the armature 25 on the Contact carrier 27 so that the armature, within certain limits, has freedom of rotation in the plane of the paper as seen in FIG. 6.

The relay 7 is a four-pole relay. Each pole unit comprises two stationary contact structures 31, each of which has a solderless terminal connector 33 disposed at its outer end and a stationary contact 35 disposed at its inner end. In each pole unit, a bridging contact structure 39 having a contact 41 at each of its two opposite ends, is provided to bridge the stationary contacts 35. The bridging contact structure 39 is supported on the cont-act carrier 27 in an opening 43, and it is maintained in position by means of a spring 45 that not only positions the bridging contact structure 39; but also acts to permit some motion of the bridging contact structure 39 upon contact engagement to thereby provide that the contacts will rnate properly when they are closed. The contacts 35, 41 are normally open contacts although they are shown in FIGS. 5 and 6 in the closed position. It is to be understood that the contacts can be made normally open or normally closed, in a manner well known in the art, depending upon the particular control requirements. Two springs 47 (only one of which is shown in FIG. 5) are provided to bias the contact carrier 27 away from the closed position seen in FIGS. 5 and 6 to thereby provide for an opening operation of the relay 7. As can be seen in FIGS. 5 and 6, a similar contact structure is provided in each of the four stalls of the relay 7, each of which stalls is separated by means of insulating barriers formed integral with the housing cover 15.

The relay or contactor 7 is shown in the energized position in FIGS. 5 and 6. In this position, the coil 19 is energized to attract the armature 25 to a position wherem the armature 25 engages the core member 17 maintaining the contact carrier 27 in the lowermost position, in which position, each of the bridging contact members 39 closes a circuit between the associated stationary contacts 35. Upon de-energization of the coil 19, the armature 25 and contact carrier 27 will be moved upwards by means of the springs 47 to thereby move the bridging contact members 39 to an open-circuit position. As was previously described, the stationary contacts 35 and bridging contacts 41 could readily be adapted to provide for normally closed contacts rather than normally open contacts in a manner well known in the art.

As can be seen in FIG. 7, the supporting plate 8 comprises a generally planar rigid plate of sheet metal material having two protrusions 51 stamped therein for supporting the relay 7 thereon. An opening 53 is provided in each of the protrusions 51 to receive fastening means (not shown) that secure the relay 7 to the sup porting plate 8. A generally circular opening 55 (FIG.. 7), having an off-set part 57, is provided in the supporting plate 8 for a reason to be hereinafter set forth.

Referring to FIGS. 1-4, the mounting plate 3 comprises a generally planar rigid plate of sheet metal material that is provided with three stations 61 for receiving and supporting three relays 7 on the mounting plate. Each of the stations 61 is defined by tour guides 63 (FIGS. 2 and 3). As can be seen in FIG. 3, each of the guides 63 comprises a generally inverted V-shaped projection that is formed on the mounting plate 3 by means of a stamping operation. Each of the stations 61 comprises hold-down means comprising three hook or ledge members 65 that are formed on the mounting plate by means of a stamping operation. Each of the stations 61 also comprises an upper opening 67 and a lower opening 69 in the mounting plate 3. The length of each of the openings 67, 69

(as measured vertically with respect to FIG. 2) -is at least as great as the dimension of the width of the open ing. As can be seen in FIG. 2, the mounting plate 3 is formed with a flat edge 71 at the periphery of each of the openings 67 and an arcuate edge 73 opposite each edge 71. Similarly, a flat edge 75 is provided at each of the openings 69 and an arcuate edge 77 is provided opposite each of the fiat edges 75. As will be understood from the following description, it is not necessary that the edges 73 and 77 be arcuate so long as the openings 67 and 69 are large enough to permit operation of a tool that is worked therein in a manner to be specifically described. Referring to FIG. 1, of the three stations 61 on the mounting plate 3, the station 61 to the left is empty; a relay 7 which is disposed on the center station 61 has not yet been moved into the fully mounted position; and a relay 7 which is disposed on the station 61 to the right is in the fully mounted position. Whenever it is desired to mount one of the control devices 6 on the mounting plate 3, the control device is set down in position between four of the guides 63 with the supporting plate 8 being disposed flatwise on the mounting plate 3. This is the position of the control device in the center station of FIG. 1. It is to be noted (FIG. 4) that the ends of the hook or ledge members 65 are up-turned to permit the mounting plate 8 to be set down under the free ends thereof in the initial position. When the control device 6 is in the position shown in the center station of FIG. 1, the upper end or edge of the supporting plate 8 is disposed such that there is an opening between the upper end and the edge 71 of the upper opening 67 in the mounting plate, which opening is just wide enough to permit insertion of a tool such as a screwdriver blade 78 (shown in section in FIG. 1). Thereafter, the screwdriver 78 is rotated either clockwise or counterclockwise from the position in which it is seen in the center station in FIG. 1 to the position in which it is seen in the righthand station in FIG. 1. During this rotation of the screwdriver 78, the supporting plate 8 and, therefore, the control device 6, is cammed downward moving rectilinearly along the mounting plate 3 between the associated guides 63 to the lower fully mounted position in which it is seen in FIG. 1, in which position the three hook members 65 firmly engage the supporting plate 8 to prevent upward removal of the control device 6. As can be seen in FIG. 4, the hook members 65 are formed with lower parts 79 that are so disposed that the clearance between the parts 79 and the flat outer surface of the mounting plate 3 is less than the thickness of the supporting plate 8 to thereby provide that the members 65 will be flexed slightly during the mounting operation so that there is an interference fit between the supporting plate 8 and the hook members 65. Thus, the control device 6 is firmly held in the fully mounted position by the hooks 65, and it must be moved rectilinearly back to the partially mounted position before it can be removed from the mounting plate 3.

- As can be seen in FIG. 1, when the electrical control device 6 is in the fully mounted position, the lower end or edge of the supporting plate 8 is so disposed that there is a space between the lower edge and the edge of the lower opening 69, which space is just large enough to admit the screwdriver 78. When the screwdriver 78 is placed in the lower opening 69 and rotated either clockwise or counterclockwise, the control device 6 will be cammed from the fully mounted position back up to the partially mounted position whereupon an operator can lift the control device 6 out from the mounting plate 3 with a slight rectilinear and outward movement. As can be seen in FIGS. 1, 2 and 7, the edges 71 and 75 of the openings 67 and 69 respectively, are generally parallel to the sides 81 (FIG. 7) of the rectangular plate 8 and generally normal to the sides 83 of the plate 8. Thus, rotation of the screwdriver affects rectilinear sliding movement of the control device 6 in a direction generally normal to the direction of the sides 81 and generally parallel to the direction of the sides 83, which movement is guided by engagement of the sides 83 with the guides 63 From the foregoing description, it can be understood that there is provided by this invention improved means for removably mounting electrical control devices in panelboards. A plurality of mounting plates are mounted on a backpanel of a panelboard, each of which mounting plates is constructed to removably support a plurality of electrical control devices that are mounted and dismounted in position without the use of fastening members such' as screws between the control devices and the mounting plate. The mounting plate and the relay supporting plate are both press-worked sheet metal members that are economical to manufacture. The station-defining guide means that guide rectilinear movement of the control device, and the hook or ledge members that are constructed to provide an interference-type support of the supporting plate, are all formed in the mounting plate by means of a stamping operation. In the disclosed embodiment, the

mounting plate is constructed with three stations for re-' ceiving three electrical control devices. It is to be understood that the mounting plate could be constructed with either more or less than three stations for receiving electrical control devices.

Since numerous changes may be made in the above described construction and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. In combination, a generally planar mounting plate having hold-down ledge means extending out of the plane of said plate, an electrical control device removably mounted on said plate and having parts thereof dispose-d under said hold-down ledge means, said electrical control device and said mounting plate being so constructed that an initial rectilinear movement of said electrical control device in a direction generally parallel to the plane of said mounting plate is necessary in order to free said parts from said hold-down means, and said electrical control device and said mounting plate comprising carn surfaces positioned to receive a tool blade therebetween that when rotated will operate against said cam surfaces to provide said initial rectilinear movement of said electrical control device.

2. In combination, a mounting plate comprising a station, said station comprising a generally planar mounting face and having hold-down ledge means extending out of the plane of said mounting face, an electrical control device mounted on said mounting face in a fully mounted position, said electrical control device comprising a generally fiat supporting plate having a first edge, said holddown ledge means biasing said supporting plate against said mounting face, said mounting plate having opening edges to thereby effect sliding means therein forming a second edge, said mounting plate and said supporting plate being constructed such that when said electrical control device is in said fully mounted position said first edge is relatively close to said second edge whereby a generally flat blade of a tool can be inserted in said opening means and rotated to earn against said first and second edges to thereby effect a sliding generally rectilinear movement of said control device from said fully mounted position to a partly mounted position, and said mounting plate and said electrical control device being constructed such that when said electrical control device is in said partly mounted position said electrical control device can be lifted away from said mounting plate.

3. In combination, a mounting plate comprising a station, said station comprising a generally planar mounting face and having hold-down ledge means extending out of the plane of said mounting face, an electrical control device mounted on said mounting face in a fully mounted position, said electrical control device comprising a generally flat supporting plate having a first edge and a second edge spaced from said first edge, said hold-down ledge means biasing said supporting plate against said mounting face, said mounting plate having a first opening means therein forming a third edge and a second opening means therein forming a fourth edge spaced from said third edge, said mounting plate and said supporting plate being constructed such that when said electrical control device is in said fully mounted position said first edge is relatively close to said third edge whereby a generally fiat blade of a tool can be inserted between said first and third edges and rotated to cam against said first and third edges to thereby effect sliding movement of said control device from said fully mounted position to a partly mounted position, said mounting plate and said electrical control device being constructed such that when said electrical control device is in said partly mounted position said second edge is relatively close to said fourth edge whereby said blade can be inserted between said third and fourth edges and rotated to cam against said second and fourth edges to thereby efiect sliding movement of said control device from said partly mounted position to said fully mounted position.

4. In combination, a mounting plate comprising a station, said station comprising a generally planar mounting face and having hold-down ledge means extending out of the plane of said mounting face, an electrical control device mounted on said mounting face in a fully mounted position, said electrical control device comprising a generally flat supporting plate having a first edge and a second edge spaced from said first edge, said hold-down ledge means biasing said supporting plate against said mounting face, said mounting plate having a first opening means therein forming a third edge and a second opening means therein forming a fourth edge spaced from said third edge, said mounting plate and said supporting plate being constructed such that when said electrical control device is in said fully mounted position said first edge is rela tively close to said third edge whereby a generally fiat blade of a tool can be inserted in said first opening means and rotated to cam against said first and third movement of said control device from said fully mounted position to a partly mounted position, said mounting plate and said electrical control device being constructed such that when said electrical control device is in said partly mounted position said second edge is relatively close to said fourth edge whereby said blade can be inserted in said second opening means and rotated to cam against said second and fourth edges to thereby efi'ect sliding movement of said control device from said partly mounted position to said fully mounted position, said station comprising guide means for guiding said electrical control device for rectilinear sliding movement between said fully mounted and partly mounted positions, and said first, second, third and fourth edges comprising straight and parallel edges extending transverse to the direction of said rectilinear sliding movement.

5. In combination, a sheet-metal type mounting plate comprising a mounting station, said station comprising a generally planar mounting face having hold-down hook means stamped therein and extending out of the plane of said mounting face in proximity to each of two opposite ends of said station, an electrical control device comprising a supporting plate and a control structure supported on said supporting plate, said supporting plate having an opening in proximity to one end thereof, said electrical control device being mounted on said station with the hook means at one end of said mounting plate passing through said opening in said supporting plate and biasing said supporting plate against said mounting face and with the hook means at the other end of said station extending over said supporting plate and biasing said supporting plate against said mounting face, said electrical control structure and said mounting plate being constructed such that said control structure can be moved out from the fully mounted position under said hook means to a partially mounted position only by means of an initial rectilinear sliding movement in a direction generally parallel to the plane of said mounting face, said station comprising guide means stamped in said mounting plate and extending out of the plane of said mount ing face at each of the two opposite sides of said station to guide said rectilinear movement of said electrical control device and said supporting plate and said mounting plate comprising facing cam edges spaced to receive a screwdriver type tool blade that when rotated will operate against said cam edges to provide said initial rectilinear movement of said electrical control structure.

6. In combination, a sheet-metal type generally planar mounting plate having hold-down hook means stamped therein extending out from the plane of said plate, an electrical control device comprising a supporting plate and a control structure supported on said supporting plate, said electrical control structure being mounted on said mounting plate in a fully mounted position with parts of said supporting plate being disposed under said hook means, said electrical control structure and said mounting plate being constructed such that said control structure can be moved into the fully mounted position and out of the fully mounted position only by means of an initial rectilinear sliding movement on said mounting plate, guide means stamped in said mounting plate and extending out of the plane of said mounting plate to guide said rectilinear sliding movement of said control structure, opening means at each of two opposite ends of said mounting plate, said opening means being positioned relative to the size of said supporting plate and relative to the fully mounted and partially mounted positions of said supporting plate such that said supporting plate can be moved from the fully mounted to the partially mounted position and from the partially mounted position to the fully mounted position by means of a rotating camming action of a tool blade disposed within the opening means.

7. In combination, a generally planar mounting plate having guide means extending from the plane thereof which guide means defines a station for receiving an electrical control device, a hook-type hold-down member at each of two opposite ends of said station extending out of the plane of said mounting plate, an electrical control device comprising a supporting plate and a control structure supported on said supporting plate, said supporting plate having an opening in proximity to one end thereof, said control device being mounted on said mounting plate at said station with one of said hook members extending over one end of said supporting plate and biasing said supporting plate against said mounting plate and the other of said hook members extending through said opening and having a part thereof disposed in engagement with said end of said supporting plate to bias said supporting plate against said mounting plate, an opening close fit 'said tool in said mounting plate at each of two opposite ends of said station, said control device being mounted in a fully mounted position on said mounting plate with only part of a first of said mounting plate openings being accessible to receive with a relatively close fit a tool blade whereby when said tool blade is disposed in said first opening and rotated said control structure will be cammed to move rectilinearly from the fully-mounted position to a partially mounted position wherein said hold-down hook means are no longer effective to securely mount said control structure, when said control structure is in said partially mounted position of the second said mounting plate openings being accessible to receive with a relatively blade whereby when said tool blade is inserted in said second opening and rotated said control device will be cammed to move rectilinearly back to said fully-mounted position.

8. In combination, a sheet-metal type generally planar mounting plate comprising a station for receiving an electrical control structure, said station being defined by four guide members stamped in said mounted plate and extending out from the plane of said mounting plate, an upper hook stamped in said mounting plate and extending out from the plane of said mounting plate, two lower hooks stamped in said mounting plate and extending out from the plane of said mounting plate, a control device mounted on said mounting plate in a fully-mounted position, said control device comprising a sheet-metal type generally planar supporting plate and a control structure mounted on said supporting plate, said supporting plate having an opening in proximity to the upper end thereof, said opening receiving said upper hook, said lower hooks being disposed over the lower end of said supporting plate and said upper hook being disposed over part of said supporting plate in proximity to the upper end of said supporting plate, each of said hooks having a part in proximity to the free end thereof that is disposed in relation to the flat surface of the mounting plate such that the dimension between said part and the fiat surface of said mounting plate is less than the thickness of said supporting plate whereby said hooks resiliently bias said parts of said supporting plate against said mounting plate, said mounting plate having an upper opening and a lower opening therein, said openings being so constructed relative to said supporting plate that when said control structure is in said fully-mounted position only a part of said lower opening is accessible to receive a generally flat tool blade which tool blade when rotated will cam said supporting plate to move said control structure rectilinearly between said guide members in a direction generally parallel to the plane of said mounting plate from the fully-mounted position to a partially mounted position, said upper opening being so disposed and constructed relative to said supporting plate that when said control structure is in said partially mounted position only a part of said upper opening is accessible to receive said generally flat tool blade which tool blade whenrotated will cam said supporting plate to move said control structure rectilinearly between said guide members in a direction generally parallel to the plane of said mounting plate from said partially mounted position to said fully-mounted position.

9. In combination, a mounting plate comprising a generally planar mounting face and having hold-down ledge means extending out of the plane of said mounting face, an electrical control device mounted on said mounting plate in a fully mounted position, said electrical control device comprising supporting plate means engaging said mounting plate, said supporting plate means being positioned under said hold-down ledge means with said holddown ledge means being in securing engagement with said supporting plate means to secure said electrical control device to said mounting plate in said fully mounted position, said electrical control device being movable on said mounting plate from said fully mounted position to a second position by means of a sliding movement in a direction generally parallel to the plane of said mounting face to permit removal of said supporting plate means from securing engagement with said hold-down ledge means, said electrical control device being movable from said second position to said fully mounted position by means of a sliding movement in a direction generally parallel to the plane of said mounting face, and said supporting plate means and said mounting plate comprising a first pair of cam surfaces positioned when said electrical control device is in said fully mounted position to receive a tool blade therebetween that when rotated will operate against said first pair of cam surfaces to cause said sliding movement from said fully mounted position to said second position, and said supporting plate means and said mounting plate comprising a second pair of cam surfaces positioned when said electrical control device is in said second position to receive a tool blade therebetween that when rotated will operate against said second pair of cam surfaces to cause said sliding movement from said second position to said fully mounted position.

10. In combination, a mounting plate comprising a generally planar mounting face and having hold-down ledge means extending out of the plane of said mounting face, an electrical control device mounted on said mounting plate in a fully mounted position, said electrical control device comprising a supporting plate and a relay supported at the back thereof on said supporting plate, said relay comprising an insulating housing and a relay mechanism supported generally within said insulating housing, said electrical control device being supported at the back thereof on said mounting plate in a fully mounted position with said supporting plate being positioned under said hold-down ledge means and with said hold-down ledge means being in frictional securing engagement with said supporting plate to secure said electrical control device to said mounting plate, said electrical control device being movable on said mounting plate from said fully mounted position to a second position by means of a sliding movement in a direction generally parallel to the plane of said mounting face to permit removal of said supporting plate from said frictional securing engagement with said hold-down ledge means, said electrical control device being movable from said second position to said fully mounted position by means of a sliding movement in a direction generally parallel to the plane of said mounting face, said supporting plate and said mounting plate comprising a first pair of cam surfaces positioned when said electrical control device is in said fully mounted position to receive a tool blade therebetween that when rotated will operate against said first pair of cam surfaces to cause said sliding movement from said fully mounted position to said second position, said supporting plate and said mounting plate comprising a second pair of cam surfaces positioned when said electrical control device is in said second position to receive a tool blade therebetween that when rotated will operate against said second cam surfaces to cause said sliding movement from said second position to said fully mounted position, and said first pair of cam surfaces being outside the front-elevational-view dimensions of said insulating housing when said electrical control device is in said fully mounted position and said second pair of cam surfaces being outside the front-elevational-view dimensions of said insulating housing when .said electrical control device is in said second position said supporting plate means to secure said electrical control device to said mounting plate in said fully mounted position, said electrical control device being movable on said mounting plate from said fully mounted position to a second position by means of a sliding movement in a direction generally parallel to the plane of said mounting face to permit removal of said supporting plate means from securing engagement with said hold-down ledge means, said electrical control device being movable from said second position to said fully mounted position by means of a sliding movement in a direction generally parallel to the plane of said mounting face, said supporting plate means and said mounting plate comprising a first pair of generally straight cam surfaces positioned in a closely spaced adjacent generally parallel relationship when said electrical control device is in said fully mounted position, said supporting plate means and said mounting plate comprising a second pair of generally straight cam surfaces positioned in a closely spaced generally parallel relationship when said electrical control device is in said second position, whereby when said electrical control device is in said fully mounted position a screwdriver type tool blade can be positioned between said first pair of cam surfaces and rotated to operate against said first pair of cam surfaces to cause said sliding movement from said fully mounted position to said second position and when said electrical control device is in said second position a screwdriver type tool blade can be positioned between said second pair of cam surfaces and rotated to cause said sliding movement from said second position to said fully mounted position.

12. In combination, a mounting plate comprising a generally planar mounting face and having hold-down ledge means extending out of the plane of said mounting face, an electrical control device mounted on said mounting plate in a fully mounted position, said electrical control device comprising a supporting plate and a relay supported at the back thereof on said supporting plate, said relay comprising an insulating housing and a relay mechanism supported generally within said insulating housing, said electrical control device being supported at the back thereof on said mounting plate in a fully mounted position with said supporting plate being positioned under said hold-down ledge means and with said hold-down ledge means being in frictional securing engagement with said supporting plate to secure said electrical control device to said mounting plate, said electrical control device being movable on said mounting plate from said fuliy mounted position to a second position by means of a sliding movement in a direction generally parallel to the plane of said mounting face to permit removal of said supporting plate from said securing engagement with said hold-down ledge means, said electrical control device being movable from said second position to said fully mounted position by means of a sliding movement in a direction generally parallel to the plane of said mounting face, said mounting plate comprising guide means engaging said supporting plate to guide said electrical control device to cause said electrical control device to move rectilinearly during said sliding movements between said first and second positions, said supporting plate and said mounting plate comprising a first pair of generally straight cam surfaces positioned in an adjacent closely spaced gen erally parallel relationship when said electrical control device is in said fully mounted position, said supporting plate and said mounting plate comprising a second pair of generally straight cam surfaces positioned in an adjacent closely spaced generally parallel relationship when said electrical controi device is in said second position, said first pair of generally straight cam surfaces and said second pair of generally straight cam surfaces extending normal to the direction of said rectilinear sliding movement of said electrical control device, said first pair of cam surfaces being outside the front-elevational-view dimensions of said insulating housing when said electrical control device is in said fully mounted position, said second pair of cam surfaces being outside the front-elevational-view dimensions of said insulating housing when said electrical control device is in said second position, whereby when said electrical control device is in said fully mounted position said first pair of cam surfaces is accessible from the front of said electrical control device and a screw driver type tool blade can be positioned between said first pair of cam surfaces and rotated to operate against said first pair of cam surfaces to cause said rectilinear sliding movement from said fully mounted position to said second position, and whereby when said electrical control device is in said second position said second pair of cam surfaces is accessible from the front of said electrical control device and a screwdriver type tool blade can be positioned between said second pair of cam surfaces and rotated to operate against said second pair of cam surfaces to cause said rectilinear sliding movement from said second position to said fully mounted position.

References tCited by the Examiner UNITED STATES PATENTS 1,247,938 11/ 1917 Curtenius 248-224 1,719,284 7/1929 Barnes 339-17 1,790,977 2/1931 De Boer 20619.5 1,874,313 8/1932 Langley 248-223 1,938,370 12/1933 Bodkin 248-223 2,027,935 1/1936 Saar 25016 2,428,320 9/1947 Platz 17|5-308 2,913,210 11/1959 Tichnor 248223 ROBERT K. SCI-IAEFER, Primary Examiner. KATHLEEN H. CLAFFY, Examiner.

H. J. RICHMAN, W. C. GARVERT,

Assistant Examiners. 

1. IN COMBINATION, A GENERALLY PLANAR MOUNTING PLATE HAVING HOLD-DOWN LEDGE MEANS EXTENDING OUT OF THE PLANE OF SAID PLATE, AN ELECTRICAL CONTROL DEVICE REMOVABLY MOUNTED ON SAID PLATE AND HAVING PARTS THEREOF DISPOSED UNDER SAID HOLD-DOWN LEDGE MEANS, SAID ELECTRICAL CONTROL DEVICE AND SAID MOUNTING PLATE BEING SO CONSTRUCTED THAT AN INITIAL RECTILINEAR MOVEMENT OF SAID ELECTRICAL CONTROL DEVICE IN A DIRECTION GENERALLY PARALLEL TO THE PLANE OF SAID MOUNTING PLATE IS NECESSARY IN ORDER TO FREE SAID PARTS FROM SAID HOLD-DOWN MEANS, AND SAID ELECTRICAL CONTROL DEVICE AND SAID MOUNTING PLATE COMPRISING CAM SURFACES POSITIONED TO RECEIVE A TOOL BLADE THEREBETWEN THAT WHEN ROTATED WILL OPERATE AGAINST SAID CAM SURFACES TO PROVIDE SAID INITIAL RECTILINEAR MOVEMENT OF SAID ELECTRICAL CONTROL DEVICE. 